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<head><meta charset="utf-8"><title>Modifying bootstrap flags without rebuild · t-compiler/help · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/index.html">t-compiler/help</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Modifying.20bootstrap.20flags.20without.20rebuild.html">Modifying bootstrap flags without rebuild</a></h3>

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<a name="235028037"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Modifying%20bootstrap%20flags%20without%20rebuild/near/235028037" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Aaron Hill <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Modifying.20bootstrap.20flags.20without.20rebuild.html#235028037">(Apr 17 2021 at 23:50)</a>:</h4>
<p>How can I pass <code>-Z time-passes</code> to the compielr during bootstrap without triggering a full rebuild?</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Modifying%20bootstrap%20flags%20without%20rebuild/near/235029780" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Modifying.20bootstrap.20flags.20without.20rebuild.html#235029780">(Apr 18 2021 at 00:21)</a>:</h4>
<p>edit src/bootstrap/bin/rustc.rs to pass it; it'll get passed only on new compilations and invisibly to cargo</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Modifying%20bootstrap%20flags%20without%20rebuild/near/235029783" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Modifying.20bootstrap.20flags.20without.20rebuild.html#235029783">(Apr 18 2021 at 00:22)</a>:</h4>
<p><span class="user-mention" data-user-id="125294">@Aaron Hill</span> ^</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/Modifying%20bootstrap%20flags%20without%20rebuild/near/235033884" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Joshua Nelson <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/Modifying.20bootstrap.20flags.20without.20rebuild.html#235033884">(Apr 18 2021 at 01:38)</a>:</h4>
<p>You could also set RUSTCFLAGS_NOT_BOOTSTRAP and see how long it takes to compile with stage 1</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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